Field of the Invention
The present invention relates to the technical field of secondary air systems for centrifugal or mixed-flow compressors, and in particular the secondary air systems for centrifugal or mixed-flow compressors of aircraft gas turbines.
Description of the Related Art
In conventional manner, a gas turbine is made up of an air inlet designed to take in an oxidizer gas, usually air, and to convey it to the inlet of a compression system that compresses the oxidizer gas. The compression system is made up of at least one compressor of mixed or centrifugal type, each centrifugal type compressor including at least one rotor mounted on a transmission shaft and at least one stator. The oxidizer gas compressed by the compression system is mixed with fuel and burnt within a combustion chamber. At least one turbine mounted on the transmission shaft converts a fraction of the kinetic energy of the gas burnt in the combustion chamber into mechanical energy serving at least to drive the compressor(s). The burnt gas exchanges heat with hot parts, e.g. the turbine(s), that it is appropriate to cool in order to limit their temperature rise.
In gas turbines of the type including at least one centrifugal or mixed-flow compressor, it is known to achieve this cooling by means of a secondary air system adapted to bleed oxidizer gas from the stator of said centrifugal or mixed-flow compressor. Bleeding is usually performed by means of a plurality of bleed orifices arranged tangentially to the flow of the fluid.
Nevertheless, the oxidizer gas may include polluting particles that act to clog, said bleed orifices at least in part. This clogging phenomenon leads to a significant reduction in the quantity of gas that is bled off by the secondary air system, and consequently it leads to a rise in the temperature in the hot parts, which in turns gives rise to a reduction in their lifetime and/or their mechanical strength.
Furthermore, the overall efficiency of the centrifugal or mixed-flow compressor may be reduced by disturbances to the flow of oxidizer gas along the rotor of the compressor, e.g. by a boundary layer of oxidizer gas in contact with the rotor becoming separated.